Heat Exchanger With Reinforced Header Plate

ABSTRACT

The invention relates to a heat exchanger ( 1 ) comprising a coolant housing ( 10 ) and a header plate ( 20 ). The header plate ( 20 ) crimps around a border ( 11 ) of the coolant housing ( 10 ) by encompassing the border ( 11 ). The header plate ( 20 ) is provided with apertures ( 22 ), each aperture ( 22 ) receiving a tube ( 30 ) for guiding coolant from or to the closed cavity ( 50 ). The heat exchanger ( 1 ) further comprises a reinforcing plate ( 40 ) extending between two opposing crimped locations on the border ( 11 ) of the coolant housing ( 10 ), and extending on the outside of the header plate ( 20 ) in view of the closed cavity ( 50 ), wherein the reinforcing plate ( 40 ) is joined, at the opposing locations, to an outer surface portion of the header plate ( 20 ), and wherein the reinforcing plate ( 40 ) is provided with at least one aperture ( 42 ) embracing one or more of the tubes ( 30 ) received by the header plate ( 20 ).

TECHNICAL FIELD

The present invention relates to a heat exchanger and in particular to aheat exchanger of the type comprising a coolant housing, a header plateand a plurality of tubes for transporting coolant from and to thecoolant housing. The invention concerns a reinforcement of the heatexchanger in order to withstand high pressures in the coolant housing.

TECHNICAL BACKGROUND

Heat exchangers are used in various applications, such as airconditioners, air compressors, gas turbines, refrigerators, andautomotive applications. Heat exchangers for automotive use may be aradiator or a charge air cooler.

Automotive and other heat exchangers may be constructed with a pair ofcoolant housings which are linked by a core leading a coolant betweenthe coolant housings. The core is typically formed by a plurality oftubes which are located adjacent each other. The tubes may be joined toa header plate which in turn is attached to the coolant housing. Thedifferent parts are typically brazed or welded together.

The above exemplified heat exchanger construction can be used forcooling internal combustion engines wherein an engine coolant iscirculated through the engine block and thereafter through the heatexchanger where it transfers heat to the through-passing air. The heatexchanger is typically located at an air intake in the front of thevehicle in order to maximize the air flow through the heat exchanger.

The heat exchanger construction may also be provided for cooling airwithin an engine system between for example a turbocharger and an engineintake.

The coolant pressure may be controlled. By increasing the coolantpressure, vaporization of the coolant can be avoided and the coolingsystem may thus increase its cooling efficiency. However, an increasedcoolant pressure puts higher pressure on the mechanical parts of thesystem, for example on the heat exchanger. In particular, joints betweenthe tubes, the header plate and the coolant housing are exposed torecurrent stress as the coolant pressure repeatedly increases anddecreases. In the long run this may cause fatigue and breakdown of thecooling system. One typical area sensitive to fatigue is the jointsinterconnecting the header plate with the coolant housing since thefluctuating coolant pressure causes the relatively weak coolant housingto repeatedly change dimensions, which changes must be accommodated bythe header plate.

One solution to this problem is to reinforce the header plate to make itmore rigid. JP9126681 provides an example of a reinforcing clip which isprovided on the header plate in a position between the tubes. The freeends of the clips are bent to follow the shape of the header body andclamp against the same. The reinforcing clip is retained by engagingunits provided on the header plate. The parts may be brazed to eachother. The solution requires modification of the header plate. Furtherit requires a complex assembly process since multiple reinforcing clipsmust be oriented and mounted in spaces having a limited access

Thus, there still exists a need for improvement with regards toreinforcement of the components in these types of heat exchangers.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved heat exchangerdesign, in particular with respect to reinforcement of the header plate.

It is a further object of the invention to provide a heat exchangerwhich facilitates the production process and which can contribute tocost-efficiency.

The above and other objects are achieved by a heat exchanger accordingto claim 1.

When pressurized coolant flows through the closed cavity, the walls ofthe coolant housing tend to bend outward due to the pressure. Inparticular, the side walls tend to bulge. The inventors have identifiedportions in the joint between the coolant housing and the header platewhich are particularly exposed to fatigue due to such bulging. In orderto strengthen the construction, a reinforcing plate is provided. Thereinforcing plate is joined to the header plate along the end portionthereof which encompasses the corner between the free edge portion andthe outer side surface portion of the border of the coolant housing.Thereby the above mentioned weak portions are strengthened andreinforced so as to increase their resistance to fatigue. Thereinforcing plate limits the displacement of the coolant housing in viewof the header plate when the heat exchanger is pressurized.

Regardless of the design of the reinforcing plate, the header plate maybe designed and manufactured in a standardized manner without care takento the reinforcement needed for a particular application. Further, theassembly of the reinforcing plate may be made with only minor effects tothe assembly line.

The reinforcing plate may be made of the same material as the rest ofthe components of the heat exchanger, i.e. typically an aluminum alloy.This means that a brazed homogenous joint may be formed along allcontact surfaces between the reinforcing plate and the header plate inthe very same brazing process that is normally used when joining allcomponents of a heat exchanger. Thus, no extra joining step is requiredwhereby the reinforcing plate easily may be integrated in the assemblyline.

Further features and advantages are achieved by embodiments disclosed inthe dependent claims.

In one embodiment, the reinforcing plate is joined to one or more tubesembraced by the apertures of the reinforcing plate. This strengthens theoverall torsional rigidity of the heat exchanger and further decreasesthe risk of fatigue related breakdowns.

In another embodiment, the reinforcing plate may be arranged to providea gap between the reinforcing plate and each of one or more tubes whichare embraced by the apertures of the reinforcing plate. This feature maybe preferred in order to provide an easy assembling of the components.Also, by a gap tolerances are made of less importance facilitating bothproduction of the reinforcing plate and assembling thereof.

Regardless of if the reinforcing plate is joined to the tubes orprovides a gap between the reinforcing plate and the tubes, theapertures of the reinforcing plate may embrace only one tube or embracea plurality of tubes.

In one embodiment, the opening defined by the border of the coolanthousing is oblong. In this case, the reinforcing plate is arranged toextend between two opposing locations on a long side of the border ofthe coolant housing. It has been found that reinforcement of the headerplate along the long side of the border of the coolant housing providesa strong overall reinforcement of the heat exchanger and also providesan improved torsional rigidity. This is particularly the case when thereinforcing plate is located along a central area of the long side.

In one embodiment, the tubes are arranged in a plurality of parallelrows. Each row comprises a plurality of tubes. The rows may extend inthe direction of the long side of the border. In such embodiment, thereinforcing plate may be arranged to embrace at least two adjacent tubesin each row. By this configuration, the reinforcing plate may extendalong as many tubes along the long side as desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to theschematic drawings.

FIG. 1 is a three-dimensional view of a typical heat exchanger in linewith the present invention.

FIG. 2 is a view of a coolant housing and a part of the core of a heatexchanger according to a first embodiment.

FIG. 3 is an exploded view of the arrangement in FIG. 2.

FIG. 4a is a side view towards the open section of the arrangement inFIG. 2.

FIG. 4b is a cross-sectional view of a section taken along line A-A inFIG. 4 a.

FIG. 5a is side view towards a short side of the arrangement in FIG. 2.

FIG. 5b is a cross-sectional view of a section taken along line B-B inFIG. 5 a.

FIG. 6 is a view of a coolant housing and a part of the core of a heatexchanger according to a second embodiment.

FIG. 7 is an exploded view of the arrangement n FIG. 6.

DETAILED DESCRIPTION

A heat exchanger 1 for heat exchange between a coolant and air isillustrated in FIG. 1. For illustrative purposes the heat exchanger isimplemented with the reinforcing plate of the invention. The heatexchanger 1 may be a radiator or a charge air cooler for use in enginecooling systems. A coolant is circulated in a closed system formed bytwo opposing coolant housings 10 and a plurality of tubes 30 extendingbetween the housings. The disclosed embodiment is provided with aplurality of vertically arranged tubes 30. It is however to beunderstood that the tubes with remained function may be horizontallyarranged. The tubes are arranged side by side in at least one row. Anumber of parallel rows, each row comprising a plurality of tubes, maybe provided.

A header plate 20 is attached to each coolant housing 10 to form aclosed cavity. The tubes 30 connect to the closed cavity throughapertures in the header plate.

During operation air is allowed to pass by the tubes 30. The tubes 30are designed to provide a large area relative its volume in order tooptimize the heat exchange. To further improve the heat exchanging area,waffled thin metal sheets 70, may be arranged between the individualtubes 30. Turbulator elements may also be provided.

The tubes 30 and the header plates 20 are preferably made of metal suchas aluminum. It is however to be understood that also other types ofmaterials may be used. In case of aluminium, the aluminum is preferablyof the type provided with a surface treatment facilitating brazing.

The coolant housings are typically made of plastics, composite or metal.

The typical process of manufacturing a brazed heat exchanger of theabove type may be briefly explained as follows: A plurality of tubes arestacked with or without intermediate distance forming waffled thin metalmaterial. The stacked plurality of tubes is kept together by arrangingtwo opposing header plates on top of the free ends of the plurality oftubes. The tubes are arranged to extend with their free ends throughapertures in the opposing header plates. The resulting stackedarrangement is thoroughly degreased and provided with a fluxing agent inorder of dissolving inevitable natural surface oxides of the aluminum.The stacked arrangement is subsequently fed through an oven where allconnecting surfaces in the stacked arrangement are brazed together toform a rigid unit with homogenous, brazed joints along all contactsurfaces. Finally a coolant housing is arranged on top of each headerplate and joined thereto. The coolant housings are typically clamped inplace by flanges on the header plate, which flanges clamp the peripheralborder of the coolant housing. A gasket is arranged between the coolanthousing and the header plate before joining the same. The resultingclamped joint will be made fluid tight by the reactive forces of thethus compressed gasket. Thereby a closed, fluid tight system is providedallowing a closed circulation of a fluid from the first coolant housing,via the plurality of tubes towards the second coolant housing.

A first embodiment of a part of an oblong arrangement 2 forming thefluid side of the heat exchanger 1 is illustrated in FIG. 2. Theillustrated part forms an end of the oblong arrangement 2. The part isillustrated as a cut-off to facilitate understanding of the design. Thecross section is representative of any part of the arrangement 2 alongeither one of the coolant housings 10 in FIG. 1.

The arrangement 2 comprises the coolant housing 10, the header plate 20and the plurality of tubes 30. It is appreciated that these componentsmay take many forms within the scope of the appended claims.

The coolant housing 10 and the header plate 20 form a closed cavity 50by that the header plate 20 covers an opening of the coolant housing 10.The tubes 30 are in communication with the closed cavity 50 by thattheir free open ends are arranged to extend into the closed cavity 50through the header plate 20.

The invention is defined by a reinforcing plate 40. The reinforcingplate 40 is arranged along and at least partly in contact with anoutside surface of the header plate 20. By outside surface is meant asurface facing away from the closed cavity 50.

The structural details of the different components in this embodimentand their attachment to each other will now be disclosed with referenceto FIGS. 3 and 4 a-4 b.

Starting with the coolant housing 10, the coolant housing 10 comprises atop wall 16 and side walls 17 extending from the top wall 16. The topwall 16 and the side walls 17 define a bowl-shaped inner cavity of thecoolant housing 10. The end of the side walls 17 forms a peripheralborder which defines an opening in the coolant housing 10. The border 11is in this embodiment a peripheral rim which extends in an outwarddirection from the closed cavity 50 along the perimeter of the coolanthousing 10. It goes without saying that the border 11 may have a numberof different designs within the scope of the invention.

The coolant housing 10 is further provided with a coolant inlet oroutlet 18. The inlet/outlet 18 is arranged to be connected to anon-disclosed coolant circulating system.

The opening of the coolant housing 10 is covered by the header plate 20for separating the closed cavity 50 of the coolant housing 10. Theheader plate 20 is also provided for connecting the tubes 30 such thatthe tubes 30 are in communication with the closed cavity 50. To thisend, the header plate 20 is provided with apertures 22. Each aperture 22receives a free open end of a tube 30.

It is important that the attachment between the header plate 20 and thecoolant housing 10 is tight in order to prevent leakage. To this end,the header plate 20 is arranged to crimp the border 11 of the coolanthousing 10. The crimping is achieved by that an end portion 23,extending from a main portion 21, of the header plate 20 encompasses aninner side surface portion 12, a free edge portion 13, an outer sidesurface portion 14 and an outer upper surface portion 15 of the border11 at opposing locations on the border 11. More precisely, the headerplate 20 crimps the border 11 along the two opposing long sides andalong the two opposing short sides. Thus, in this embodiment, the headerplate 20 is arranged to crimp around the border on at least two opposinglocations.

By inner side surface portion 12 of the coolant housing 10 within thescope of the invention is meant a surface portion of the border 11constituting an elongation of the inner envelope surface of the coolanthousing 10. The inner envelope surface of the coolant housing 10 facesthe closed cavity 50.

By outer side surface portionl4 of the coolant housing 10 within thescope of the invention is meant a surface portion of the borderconstituting an elongation of the outer envelope side surface of thecoolant housing 10. The outer envelope surface of the coolant housing 10faces away from the closed cavity 50.

By free edge portion 13 of the coolant housing 10 within the scope ofthe invention is meant a surface portion of the border located betweenthe inner and outer envelope surfaces of the coolant housing 10.

By outer upper surface portion 15 of the border within the scope of theinvention is meant a surface portion of the border facing away from theheader plate 20.

By encompassing is meant that the end portion 23 of the header plate 20follows the surface portions of the coolant housing 10, however it isnot necessary that the end portion 23 of the header plate 20 abuts thesurface along the whole surface portion of the coolant housing 10. Thus,the contact between the end portion 23 of the header plate 20 and theouter side surface portion 14 of the coolant housing 10 may becontinuous or discontinuous along the circumference of the coolanthousing 10 as long as a fluid tight sealing is achieved. An intermediateflexible sealing may be arranged where necessary.

In the disclosed embodiment, the end portion 23 of the header plate 20abuts two opposing surface portions of the border 11, being the innerside surface portion 12, the outer side surface portion 14 and the outerupper surface portion 15, so as to achieve the crimping effect. It isappreciated that the crimping effect may be achieved by differentconfigurations of the header plate 20 and its end portion 23. Forexample, the header plate 20 may encompass only the free edge portion 13and the outer side surface portion 14 at each opposing location to pressthe opposing locations of the border 11 toward each other. In otherwords, the header plate 20 may have a clip-like form and function. Otherconfigurations are also obvious to the skilled person.

The header plate 20 comprises end flaps 24 which encompass the outerupper surface portion 15 of the border 11. This feature strengthens thecrimping and thus further increases the tightening of the joint betweenthe header plate 20 and the coolant housing 10. By a non-disclosedgasket being arranged between the header plate 20 and the border 11 suchgasket will be compressed by the crimping and the reaction forceresulting from the compressed gasket will ensure a fluid tight joint andprevent any significant movements.

During operation, when pressurized coolant flows through the closedcavity 50, the coolant housing 10 tends to bend outward due to thepressure. In particular, the side walls 17 tend to bulge. The bending istypically cyclic, meaning that over time there is a risk of fatigue. Theinventors have identified two weak portions on the header plate 20 whichare particularly exposed to fatigue stress at high coolant pressures.The first portion is the corner C1 between the main portion 21 and thefirst part of the end portion 23 which encompasses the inner sidesurface portion 12 of the coolant housing 10 and thereby the innerenvelope surface portion of the coolant housing 10. The second portionis the corner C2 in the end portion 23 which encompasses the cornerbetween the free edge portion 13 of the coolant housing 10 and the outerside surface portion 14 of the coolant housing 10, i.e. the innerenvelope surface portion of the coolant housing 10. Moreover, it hasbeen realized that the part of the end portion 23 which runs along theouter side surface portion 14 of the coolant housing 10, i.e. the outerenvelope surface portion tends to bend outward due to the border 11being pressed in an outward direction. Even if the end portion 23 doesnot break, it will be exposed to wear over time with the consequencethat the crimping loosens thus un-tightening the joint between thecoolant housing 10 and the header plate 20. There is also a risk thatthe cyclic stress causes fatigue in the brazed joints between the headerplate 20 and the tubes 30.

In order to strengthen the design, the invention provides a reinforcingplate 40. The reinforcing plate 40 comprises a main portion 41 forming abottom and at least two opposing end portions 43.

The reinforcing plate 40 is formed by stamped sheet metal and ispreferably made of the same material as the header plate 20 and thetubes 30 to facilitate joining there between.

The reinforcing plate 40 is arranged on an outside surface of the headerplate 20, and extends between two opposing crimped locations on theborder 11 of the coolant hosing 10.

The reinforcing plate 40 is in contact with and joined to the headerplate 20 at least at two positions: one at each crimped location on theborder 11. More precisely, the reinforcing plate 40 is arranged incontact with and joined to each of the end portions 23 of the headerplate 12. The joint is arranged along at least the part of the endportion 23 which encompasses the corner C2 between the free edge portion13 of the coolant housing 10 and the outer side surface portion 14 ofthe border 11.

By that the reinforcing plate 40 is joined to this particular part ofthe header plate 20, the above mentioned weak corners C1 and C2 arestrengthened and reinforced so as to increase their resistance tofatigue due to high cyclic pressures in the coolant housing 10. Thereinforcing plate 40 limits the displacement of the header plate 20 andof the coolant housing 10 when the latter is pressurized. The limiteddisplacement reduces stresses on the coolant housing 10, the headerplate 20 and the tubes 30 and also on all joints between thesecomponents.

The end portions 43 of the reinforcing plate 40 are curved so as tofollow the curvature of the end portions 23 of the header plate 20. Thereinforcing plate 40 may be joined to the header plate 20 along otherportions as well. In the disclosed embodiment, there is by way ofexample a joint between the header plate 20 and the reinforcing plate 40along the main portion 41 of the reinforcing plate 40 and the headerplate 20.

The height H of the opposing end portions 43 of the reinforcing plate 40may vary. As a minimum the reinforcing plate 40 should extend around thecorner C2 of the header plate 20 and at least along a portion of the endportion 23 of the header plate 20. It must however not necessarily havethe same height and extension as the end portion 23 of the header plate20.

The reinforcing plate 40 comprises apertures 42. In the disclosedembodiment, each aperture 42 embraces a single tube 30. By the termembrace is within the scope of the invention meant that the tube 30 islocated in the aperture 42, however the tube 30 need not abut thereinforcing plate 40 as will be illustrated further on. In thisembodiment, however, the reinforcing plate 40 is arranged in contactwith and joined to each of the tubes 30. This feature strengthens thetorsional rigidity of the heat exchanger as such and may further add tothe reinforcement of the relevant corners C1 and C2.

In the disclosed embodiment, the apertures 42 have peripheral rims 42 awhich give an extra support and contact surface to the tubes 30. Theheader plate 20 comprises similar peripheral rims 22 a.

The joint in the contact surfaces between the header plate 20 and thereinforcing plate 40 are preferably brazed, homogenous joints, whichjoints are formed in the very same process step as is previouslydisclosed for being used when brazing the stacked components making upthe heat exchanger in FIG. 1.

A two-dimensional view toward a short side end of the arrangement 2 inFIG. 2 is illustrated in FIG. 5a . A section taken along the line B-B isillustrated in FIG. 5 b.

The reinforcing plate 40 extends between two opposing locations, beingcrimped by the header plate 20, on the long side of the border 11 of thecoolant housing 10. This positioning of the reinforcing plate 40 may beadvantageous when the opening of the coolant housing 10 has an oblongextension with a length considerably exceeding the thickness of the heatexchanger. It has been found that reinforcement of the header plate 20along the long side of the border 11 of the coolant housing 10, inparticular along a central area of the long side, provides a strongreinforcement of the heat exchanger. By central area is meant that thereinforcing plate 40 embraces tubes 30 which are not located at the endof the long side, i.e. adjacent the short side of the order 11.

The reinforcing plate 40 could in other embodiments (not disclosed) alsoextend between two opposing locations on the short sides of the border11 of the coolant housing 10.

A second embodiment of a part of the arrangement 3 forming the fluidside of the heat exchanger 1 is illustrated in FIGS. 6 and 7. Thecomponents which are similar to the ones illustrated in the firstembodiment are provided with the same reference numerals.

The arrangement 3 comprises a reinforcing plate 60 which has a slightlydifferent configuration than the first embodiment of the reinforcingplate 40. The reinforcing plate 60 comprises a main portion 61 forming abottom and two opposing end portions 63 which extend from the mainportion 61.

The reinforcing plate 60 is joined to the header plate in similar manneras in the first embodiment. In other words, the reinforcing plate 60 isjoined to each of the end portions 23 of the header plate 20. The jointis arranged along at least the part of the end portion 23 whichencompasses the corner C2 between the free edge portion 13 and the outerside surface portion 14 of the border 11. Similar to the firstembodiment, the end portions 63 are curved so as to follow the curvatureof the end portions 23 of the header plate 20.

The reinforcing plate 60 is provided with apertures 62. Contrary to thefirst embodiment, each aperture 62 encompasses a pair of adjacent tubes30. In this embodiment, the tubes 30 are located in a plurality of rowsbeing two rows in the illustrated case. The rows are located inparallel. Each row comprises a plurality of tubes 30. The illustratedpart of the arrangement 3 shows three tubes 3 in each row. Each rowextends in the direction of the long side of the border 11 whichprovides an oblong opening of the coolant housing 10.

The reinforcing plate 60 embraces adjacent tubes 30 in adjacent rows.Moreover, the single reinforcing plate 60 is provided with a pluralityof apertures 62 which together embrace a plurality of tubes 30 along therows.

The reinforcing plate 60 differs from the reinforcing plate 40 of thefirst embodiment also in that it is not joined to the tubes 30. On thecontrary, the reinforcing plate 60 is arranged to provide a gap betweenthe reinforcing plate 60 and each of the tubes 30 embraced by theapertures 62. This feature may be preferred in order to facilitateassembling of the components. Further, the tolerances of the apertures62 of the reinforcing plate 60 may be given a reduced importance.

The two above disclosed embodiments exemplifies the great variety ofdesigns of the reinforcing plate 40 and 60 that is feasible within thescope of the invention. Regardless of the design of the reinforcingplate 40, 60, the header plate 20 may be designed and manufactured in astandardized manner without care taken to the type of reinforcing plate40, 60 to be used.

The reinforcing plate may be chosen and added during the assembly of theheat exchanger with only minor effect on the assembly line.

It is to be understood that a plurality of reinforcing plates 40, 60 maybe arranged side by side along the header plate 20. The reinforcingplates 40, 60 may be arranged side by side in contact with each other orbe arranged with an intermediate distance.

By making the reinforcing plates 40, 60 in the very same material as therest of the heat exchanger with the exception of the coolant housingwhich typically is made of plastics, the reinforcing plate 40, 60requires no separate joining step but will be brazed to adjacentcomponents being in contact therewith during the conventional brazingstep. Further, by being of the same material as the header plates 20 andthe tubes 30, the reinforcing plates 40, 60 will move thermally togetherwith the rest of the heat exchanger causing no additional stress to thebrazed joints.

It is appreciated that the embodiments of the invention as disclosedabove may be altered in different ways within the scope of the appendedclaims. For example, the number of apertures 42 and 62 and the geometrythereof may vary depending on the type of tubes and their geometry.Another example is that the border may take any suitable form. It isappreciated that the reinforcing plate according to the invention can beused in any type of heat exchanger where the coolant housings areattached to the header plate by crimping, brazing, welding or the like.

1. Heat exchanger comprising: a coolant housing having a border whichdefines an opening; a header plate arranged to cover the opening;wherein the header plate crimps the border of the coolant housing byencompassing a free edge portion, an outer side surface portion and anouter upper surface portion on at least two opposing locations on theborder; whereby a closed cavity for coolant is defined by the coolanthousing and the header plate; and wherein the header plate is providedwith apertures, each aperture receiving a tube for guiding coolant fromor to the closed cavity; the heat exchanger further comprising: areinforcing plate extending between two opposing locations on the borderof the coolant housing, and extending on the outside of the header platein view of the closed cavity, the reinforcing plate being made of thesame material as the header plate and the tubes; wherein the reinforcingplate is joined, at each of said opposing locations, to an outer surfaceportion of the header plate encompassing a corner between the free edgeportion and the outer side surface portion of the border; wherein thereinforcing plate is provided with at least one aperture embracing oneor more of the tubes which are received by the header plate; and whereinthe reinforcing plate is arranged to provide a gap between thereinforcing plate and each of one or more tubes embraced by theapertures of the reinforcing plate.
 2. The heat exchanger according toclaim 1, wherein the reinforcing plate is joined to one or more tubesembraced by the apertures of the reinforcing plate.
 3. (canceled)
 4. Theheat exchanger according to claim 1, wherein each of the at least oneapertures of the reinforcing plate embraces only one tube received bythe header plate.
 5. The heat exchanger according to claim 1, whereineach of the at least one apertures of the reinforcing plate embraces aplurality of tubes received by the header plate.
 6. The heat exchangeraccording to claim 1, wherein the opening defined by the border isoblong; and wherein the reinforcing plate is arranged to extend betweentwo opposing locations on a long side of the border.
 7. The heatexchanger according to claim 6, wherein the tubes are arranged in aplurality of parallel rows, each row comprising a plurality of tubes;wherein the rows extend in the direction of the long side of the border;and wherein the reinforcing plate embraces at least two adjacent tubesin each row.
 8. The heat exchanger according to claim 6, wherein thereinforcing plate is arranged at a central area of the header plate withrespect to the long side of the border.
 9. The heat exchanger accordingto claim 1, wherein the tubes have an oblong cross-section and arearranged with the same orientation, and wherein the reinforcing plateextends along the long sides of the tubes.
 10. The heat exchangeraccording to claim 1, wherein the reinforcing plate is joined to theheader plate by brazing.
 11. The heat exchanger according to claim 1,wherein the header plate encompasses also an inner side surface portionat each of said two opposing locations on the border.
 12. The heatexchanger according to claim 1, wherein the coolant housing comprises atop wall and side walls which extend from the top wall, the top wall andside walls defining a bowl-shaped inner space of the coolant housing.13. The heat exchanger according to claim 7, wherein the reinforcingplate is arranged at a central area of the header plate with respect tothe long side of the border.